Research suggests that breathing disorder could exacerbate heart disease

By Randy DotingaHealthDay Reporter

Sleep apnea leads to interrupted breathing during sleep. In their study, the researchers found that patients with the condition who had a form of the heart procedure called angioplasty were much more likely to suffer heart attacks or strokes after their procedure.

The big difference held up even when the researchers adjusted their findings so they wouldn't be thrown off by factors like obesity and high blood pressure, which are common in these patients.

While the study did not prove sleep apnea caused heart disease to worsen, the authors think the first one probably exacerbates the second one.

"For cardiologists inserting stents for coronary artery disease, it is important to screen the patients for obstructive sleep apnea," said study author Dr. Lee Chi-Hang.

"And patients who have been diagnosed with sleep apnea should know about the strong relationship between sleep apnea and heart disease," added Chi-Hang, a senior consultant in the department of cardiology at the National University of Singapore Heart Center.

For the study, the researchers tracked just over 1,300 patients from Brazil, China, India, Myanmar and Singapore who had undergone angioplasty with stents. In these procedures, surgeons thread catheters through vessels and clear blockages by implanting stents designed to keep arteries open.

Almost 60 percent of the patients were overweight or obese, and 45 percent were diagnosed with sleep apnea.

The researchers followed the patients for a median of two years. Of the patients, 141 (11 percent) suffered a stroke, heart attack or needed another procedure. Out of those patients, 24 died.

But, these problems only occurred in 8 percent of patients without sleep apnea.

Chi-Hang said sleep apnea appears to be the culprit, especially in light of the "ample data" in studies over the past two decades that has linked it to heart disease.

Sleep apnea appears to contribute to cardiac illness by robbing people of oxygen, Chi-Hang said, a process that can lead to surges in blood pressure and inflammation. These, in turn, can harm the lining of blood vessels, thicken blood and make the heart struggle, he explained.

Chi-Hang said doctors should screen angioplasty-with-stent patients for sleep apnea. Patients with the sleep condition who have daytime sleepiness should get treatment via CPAP (continuous positive airway pressure) breathing machines, he said.

However, only 1 percent of those diagnosed with sleep apnea were being treated via CPAP by the end of the study, as many patients won't accept treatment with the breathing machines, he added.

Moving forward, the National University Heart Center Singapore is planning a study to provide insight into whether certain heart patients should undergo testing for sleep apnea, Chi-Hang said.

Dr. Sanja Jelic, an associate professor of medicine at Columbia University Medical Center in New York City, said "the mystery remains whether treatment of sleep apnea reduces cardiovascular risk."

The research has been limited because only about 30 percent to 40 percent of patients who try the breathing devices keep using them after a year, she explained.

Jelic said it may be possible to better understand the connection with a controlled clinical trial. But, it would be dangerous to assign some sleep apnea patients with daytime sleepiness to not undergo treatment just to compare them to those who do get treatment.

Meanwhile, Jelic said, "every patient with cardiovascular disease should be screened for sleep apnea by answering questions during the doctor's visit."

The findings were to be presented Monday at the American Thoracic Society annual meeting in San Francisco. Studies released at conferences should be considered preliminary until they are published in medical journals after peer review.